Plate heat exchangers are one of several components in cooling and heating systems. They are an important component as the plate heat exchangers are used to place two or more fluids in heat exchange relationship with one another, acting as either a condenser or evaporator, depending upon the desired application. In other words, one of two or more fluids is preferably condensed or evaporated. Preferably, one of the fluids is a refrigerant. The plate heat exchangers are typically used in combination with a compressor, expansion valves and blowers to heat or cool a space. Plate heat exchangers are desirable to use due to their compact construction and convenient installation.
The plate heat exchanger typically is a sealed device that has an inlet and an outlet for each of the two or more fluids, which are isolated from one another, that circulate through the heat exchanger. The sealed device typically includes a plurality of pressed plates, the patterns of the pressed plates typically taking the form of a herringbone defining “V-ridge” cross sections of alternating apexes, with apertures being formed adjacent the ends in the pressed plates to permit flow of the two or more fluids. The plates are configured so that by alternately rotating the plates end-for-end, the apertures are configured to provide separate flow passages for each of the fluids between plate pairs, one fluid possibly having multiple flow passages between a predetermined number of plate pairs. The end-for-end rotation also provides opposed herringbone patterns between adjacent plate pairs. By virtue of this staggered arrangement, the opposed herringbone patterns intermittently contact each other along the respective apexes of the V-ridges of the herringbone patterns, each contact region being referred to as a node. This staggered interface between each plate pair defines a tortuous flow passage of constantly changing direction and cross-section, providing more efficient thermal communication between different fluids flowing along adjacent flow passages while maximizing fluid contact with the surfaces of the plates.
The above geometry exhibits improved thermal communication values, typically referred to as a refrigerant side heat transfer coefficient, of approximately 380 BTU/° F./ft2/hr at typical design conditions to the heat transfer fluids passing through the plate heat exchanger. However, the value of this coefficient is significantly less than that achieved by other heat exchanger constructions, such as by enhanced tubes having a first fluid or refrigerant flowing therethrough, the tubes being passed through a vessel containing a second fluid passing over the tubes, and vice versa.
Therefore, there is a need for a plate heat exchanger construction having improved heat transfer coefficient values.